The invention relates to a device and a method for the manufacture of circumferentially closed tubular tube bodies.
Manufacturing plants for the manufacture of tubes are known from the prior art. For the manufacture of tube bodies, a web-shaped substrate is conveyed by conveying means, for example rolls and/or rollers, in a conveying direction and is formed by tube forming means, for example by rolls, rollers and/or stationary deflector plates, into a tubular form around a cylindrical mandrel. In so doing, the two marginal regions, which respectively adjoin one of the longitudinal edges of the substrate web, contact one another, in the tubular form in a contact region, for instance in the form of an overlapping region, in which the two marginal regions overlap one another, or a contact position, for instance in the form of an abutting edge, in which the two longitudinal edges of the substrate lie against one another (wherein in the following the terms “contact region” and “contact position” are to be deemed to be synonymous and interchangeable). In this contact region, the two marginal regions are welded to one another with the formation of a weld seam, for example by means of a high frequency welding device.
By several different influences, the contact region can move away from the welding position which is defined by the welding device, frequently resulting in defective tube bodies. When the contact region runs adjacent to or only partially through the welding region, this can result in a deficient tightness and/or pressure resistance of the tube bodies.
A travelling of the contact region in circumferential direction occurs for example on the exchanging of the substrate web, in the case of substrates which are rolled nonhomogeneously, or in the case of fluctuating tensile load of the substrate web. In order to counteract these disruptive position fluctuations, systems are used which attempt to keep constant the position of the substrate web transversely to the conveying direction before the shaping process into the tubular form, i.e. before the shaping region. For this, ultrasonic sensors are used for example, which detect at least one longitudinal edge of the substrate web, and positioning means e.g. in the form of a pivotable roller, which can correct a deviation of the edge position from the required position, if necessary.
This type of monitoring indeed takes into account selectively the edge position of the substrate web at the detection site, but not the alignment of the substrate web, i.e. the angle at which the substrate web runs past the edge sensor, for which reason, despite keeping a required edge position, the position of the contact region at the welding means can deviate considerably from the welding position. Also, the influences are not taken into account which occur between the position of the edge sensor and the welding position. Such influences include for example a fluctuation in the web tension and in the web course, owing to the friction between the mandrel and the substrate or respectively by slippage of the substrate or by position fluctuations of a shaping means, such as e.g. a forming belt. Therefore, despite the monitoring and correction of the web position to a required position, deviation can occur of contact region to welding position.
Currently, these disruptive influences are balanced out by the required position of the web edge being adjusted manually by an operator, so that the contact position again falls into the welding position. This is costly, is time-consuming (therefore generates waste) and requires experienced personnel who are in addition frequently involved periodically in monitoring tasks.
From JP 59 230727 A outside the field of the manufacture of tube bodies, a device is known which shapes a film strip into a cylindrical form and in this form welds two edges of the film strip which overlap one another. The device comprises sensor means which detect a deviation of the edges of the film strip, and positioning means which can move the film strip laterally to the transport direction of the film.
From JP 5 250955 A a device is known for the sheathing of a metal core with an insulation material for the manufacture of an electrically conductive cable. The device comprises an ultrasonic sensor, which establishes the position of one of the edges of the insulation material, and adjusting means, which influence the circumferential position of the edge so that this is kept as constant as possible.
From WO 03/024694 A1 it is known, in a device for the manufacture of tube bodies, to check an overlapping region after welding by an infrared line sensor for the maintaining of a predetermined temperature profile and, in the case of deviations, a signal is emitted for the rotation of a shaping funnel with a guide wedge arranged in the shaping region.
From WO 2006/013171 A1 a device is known for the manufacture of tubular bags, in which a film web is shaped by a shaping shoulder and two edges of the film web are connected with one another. In this device, the circumferential position of the overlapping edges is constant, wherein the radial extent of the respective edges can be adjusted by adjusting the position of the film web before the shaping means.